Support callable base_path in FileUploadField

Upgrade moment.js to 2.8.4

Upgrade select2 to 3.5.2

Upgrade jQuery to 2.1.1

sqla: respect required validator on relations

Fix Time/DateTime Equals Filters For SQLAlchemy+SQLite

* Added an ItemsRequired validator
* Make inline relation check form_args
* Don't apply Optional validator if Required validator was specified
* Test case: many emails for each user, but each user must have
  at least one email

Use bootstrap-daterangepicker instead of bootstrap-datetimepicker and add Time filter support

WForms2 compatibility – resumed

Set cover-package for running tests

fix greater/smaller filters for pymongo

Fix incorrect usage of NotImplemented constant

`NotImplemented` is a constant singleton used in rich comparison
overloading. It is not callable, and is not an exception.
`NotImplementedError` is a built in exception.

WTForms 2 compatibility

Replaced deprecated TextField with StringField

Typo fix in form_rules.rst